Drug delivery devices are generally known for the administration of a medicinal product, for example insulin, but also for other medicinal products for self-administration by a patient. Therefore, the drug delivery devices should be safe and comfortable in use and should dispense an exact dose of a medicinal product. Most of the drug delivery devices are pen-type injectors which can dispense a pre-set dose of a medicinal product.
In some cases it is necessary for the patient to get an exact volume of a certain medicinal product. In most commercially available drug delivery devices there are many sources of error for dispensing inaccuracy. One is for example the dripping out of the needle after injection and therefore the need to keep the needle in the skin after injection.